Scanning probe lithography for electrode surface modification

Application of scanning probe microscopy (SPM) to a nanometer-scale lithographic tool is demonstrated. An organosilane monolayer composed of octadecylsilyl [CH3(CH2)(17)Si=] groups was prepared by chemical vapor deposition and served as a resist material for scanning probe lithography. Using an atomic force microscope (AFM) with an electrically conductive probe, the monolayer deposited on a Si substrate was patterned by flowing current through the AFM-probe \ monolayer junction. The pattern thus fabricated on the monolayer was transferred to the substrate Si by chemical etching in an aqueous solution of NH4F and H2O2. The etching proceeded area-selectively in the regions where the probe had passed, since, in these regions, the monolayer had been degraded electrochemically. Furthermore, we have developed a nanofabrication method that uses the patterned organosilane monolayer as a template for pattern transfer to a Au nanostructure. The patterned organosilane monolayer was first etched in HF solution in order to expose the substrate Si in the monolayer-degraded region. The HF-etched sample was next treated in a Au electrode plating bath. In this plating, deposition of Au proceeded selectively on the exposed Si area while the surrounding undegraded monolayer surface remained free of deposits. The probe-scanned pattern was transferred to a Au pattern through this area-selective electrode plating. (C) 1999 Elsevier Science S.A. All rights reserved.